When filling beverages or other liquids into containers, such as glass or plastic containers, it may be necessary to inspect the filled and closed containers for foreign bodies. During the filling process, e.g. individual machine parts, such as nuts, screws or the like, may get into the containers. Such large foreign bodies are comparatively easy to detect.
Foreign bodies that are difficult to detect are fine particles such as transparent glass fragments. Since containers often have scuffs or scratches on their bottom, it is often impossible to unequivocally identify glass fragments in comparison therewith.
For detecting such foreign bodies, WO 2004/053471 discloses a device for inspecting filled and closed receptacles. This publication discloses that the containers are caused to rotate, so that also the content of the container, including the glass fragments, will rotate. After the container has been brought to a stop, the liquid including the glass fragments will continue to rotate, so that the fragments can easily be detected by respective camera recordings.
Causing the content of a container to move through rotation of the container necessitates a comparatively large expenditure of time, so that high target throughput rates will here lead to a comparatively high investment in machinery.
DE 10 2004 051961 A1 discloses an apparatus for inspecting a filled container for foreign bodies. In the case of this apparatus the filled and closed container can be held in a movable holding device and moved continuously on a circulation path, preferably together with an inspection camera which is adapted to be moved along with the holding device. Making use of a vibration unit for producing vibrations in the container, foreign bodies, such as fine glass fragments, on the bottom of the container are caused to move and can thus be recorded with the inspection camera.
A disadvantage of this apparatus is the technical outlay entailed by image processing as well as the limitation to transparent containers and liquids.
Also DE 10 2010 053 771 A1 discloses an apparatus for inspecting a filled container for foreign bodies. In this apparatus the containers are mechanically excited via the holding device, so that the liquid contained therein, including foreign bodies that may be contained in the liquid, moves relative to the container wall. The signals that may result from impacts of foreign bodies on the housing wall are detected by a piezosensor integrated in the holding device. The signals provided by the piezosensor are transmitted to an analysis unit by means of a slip ring or by wireless transmission.
However, the integration of the piezosensors in the holding device, which must also be configured for mechanical excitation, requires a substantial constructional outlay that is opposed to a reasonably-priced solution.